1. Field of the Invention
The present invention relates to an engine air-oil separator provided in a head cover for separating oil contents in blow-by gases that are recirculated to an intake system of the engine.
2. Description of the Related Art
Crankcase ventilation has been implemented to suppress the deterioration of oil within an oil pan of an engine and to suppress the pressure fluctuation within a crankcase due to reciprocating movements of pistons in the engine. Unburned products are contained in breather air (blow-by gases) generated from the interior of the crankcase, and in an automotive engine, these blow-by gases are then recirculated into intake air for re-combustion.
In addition, lubricating oil mists are contained in breather air from the interior of the crankcase, and re-combustion of the breather air containing the lubricating oil mists produces adverse effects for cleaning of exhaust air, and therefore, to cope with this, an air-oil separator is provided in an engine for separating oil contents in the breather air.
An air-oil separator is well known in, for example, Japanese Patent Unexamined Publication No. Hei.10-220215 which is constructed such that a centrifugal separation chamber is attached to an upper surface of a head cover for producing swirl flows in blow-by gases that are recirculated to an intake system of an engine.
According to the related art disclosed in the above publication, however, since the centrifugal separation chamber protrudes upwardly from the upper surface of the head cover, the height of the engine is increased.
The invention was made with a view to solving the inconvenience in the above related art, and an object of the present invention is to provide an engine air-oil separator which is improved so that the outwardly protruding amount of a cylinder head can be reduced.
With a view to attaining the object, according to a first aspect of the invention, there is provided an engine air-oil separator provided in a head cover (1) for separating oil contents in blow-by gases that are recirculated to an intake system, wherein a centrifugal separation chamber (7) for generating swirl flows in blow-by gases is formed integrally with the head cover by a wall (a circumferential wall 14 in an embodiment) protruding inwardly from an internal surface of an external wall of the head cover. According to this construction, since the centrifugal separation chamber can be embedded inside the head cover, space saving can be promoted.
Further, according to a second aspect of the invention, there is provided an engine air-oil separator as set in the first aspect of the invention, wherein an outer end of said centrifugal separation chamber opens in the external wall of the head cover, and a blow-by gas inlet passageway (a U-shaped groove 29 in the embodiment) communicating with the interior of the centrifugal separation chamber is formed in a joint surface between a lid member (a flange portion 21 in the embodiment) for closing the opening and the head cover by recessing at least an external surface (an attachment seat 16 in the embodiment) of the head cover.
Furthermore, according to a third aspect of the invention, there is provided an air-oil separator as set forth in the second aspect of the invention, wherein a boss portion (31) provided by the side of the inlet passageway in the head cover, the boss portion having provided therein threaded holes (30) in which bolts for fixing the lid member are screwed for attachment therein.